Repair bottom plate, T-shaped connector base plate and oil storage tank bottom plate repair welding process

Abstract

The invention belongs to the technical field of oil storage tank bottom plate repair, and particularly relates to a repair bottom plate, a T-shaped connector base plate and an oil storage tank bottom plate repair welding process. The oil storage tank bottom plate welding joint structure with the self-backing plate function is adopted for welding, the performance is guaranteed, meanwhile, the material use cost can be greatly reduced, the workload is reduced, and welding deformation is reduced. By the adoption of the T-shaped connector base plate, welding deformation during local repairing of the large flat-bottom storage tank bottom plate can be effectively reduced, stress concentration is reduced, the flatness of the whole bottom plate after welding is good, and obvious concave-convex deformation is not found.

Description

Technical Field

[0001] The invention belongs to the technical field of oil tank bottom plate repair, and in particular relates to a repair bottom plate, a T-joint pad and an oil tank bottom plate repair welding process. Background Art

[0002] With the rapid development of oil storage and transportation projects, oil and gas storage and transportation facilities tend to be large-scale, and large storage tanks are increasingly widely used. The bottom plate of a large storage tank is composed of multiple strip-shaped middle plates and multiple arch-shaped edge plates, which is the part of the entire tank that is subjected to the greatest force. The bottom of the tank will partially sink during long-term use, causing surface corrosion and pitting corrosion under the flat bottom of the tank. In the case of severe corrosion, the bottom plate will leak and the tank will be forced to be shut down for maintenance.

[0003] In traditional maintenance, the entire bottom plate is usually replaced, which requires a large amount of construction, high cost and a long manufacturing cycle. In order to solve the problem of severe corrosion in specific parts of the tank bottom plate, the corroded steel plate can be partially replaced, and the newly replaced steel plate can be connected to the retained part of the bottom plate by welding. However, welding deformation and stress concentration are prone to occur during the welding process, which reduces the fatigue strength of the welded structure and causes failure behaviors such as stress cracking of the joints. In the maintenance of the tank bottom plate, the control of welding deformation is particularly important to ensure the geometric dimensions of the oil tank, prevent stress concentration, and improve the forming quality. Controlling the welding deformation of the tank bottom plate is also one of the main technical problems to be solved in large-scale tank manufacturing.

[0004] The existing patents related to the welding of the bottom plate of large oil and gas storage tanks are mostly concentrated on the overall construction of the bottom plate, including the arrangement of the middle plate steel plate and the adjustment of the welding sequence. The patent for the repair of the bottom plate is to replace the bottom plate as a whole, with the same process as the construction, and there is no design for partial replacement of the failed steel plate, which requires large construction, high cost and long manufacturing cycle. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, the present invention provides a repair bottom plate, a T-joint pad, and a welding process for repairing the bottom plate of an oil tank. The present invention adopts a welding joint structure of the bottom plate of an oil tank with a self-pad function for welding, which can greatly reduce the material use cost and workload while ensuring performance, and reduce welding deformation. The present invention adopts a T-joint pad, which can effectively reduce the welding deformation during the local repair of the bottom plate of a large flat-bottomed storage tank, reduce stress concentration, and the flatness of the entire bottom plate after welding is good, and no obvious concave-convex deformation is found.

[0006] The technical solution provided by the present invention is as follows:

[0007] An oil storage tank bottom plate comprises a bottom plate body, wherein the bottom plate body has a replacement opening cut out therein, the bottom of each side of the replacement opening has a horizontal plate-shaped protrusion, and the upper part of each side of the replacement opening is a slope structure.

[0008] Based on the above technical solution, the horizontal plate-like protrusions arranged at the bottom of the side of the bottom plate body replacement opening of the oil storage tank bottom plate have the function of a pad, so that the oil storage tank bottom plate has a self-pad function. Such a welded joint structure can reduce the use of pads while ensuring performance, thereby reducing the amount of material used. At the same time, the upper part of the side of the bottom plate body replacement opening is processed into a slope structure, which can cooperate with the repair bottom plate to form an unpenetrated V-shaped groove.

[0009] Specifically, the replacement opening is rectangular.

[0010] Specifically, the slope of the slope structure is 65-67.5°, which can reduce the groove angle as much as possible while facilitating welding and ensuring penetration.

[0011] Specifically, the thickness of the plate-like protrusion is 10% to 15% of the thickness of the bottom plate body, which ensures that the backing plate has a certain thickness and the strength of the welded joint is guaranteed.

[0012] Specifically, the width of the plate-shaped protrusion is 20 to 25 mm.

[0013] The present invention further provides a repair base plate, comprising a repair plate body, wherein the upper portion of the side surface of the repair plate body is provided with a right-angled trapezoidal protrusion.

[0014] Based on the above technical solution, the slope of the right-angled trapezoidal protrusion of the repair plate body can cooperate with the oil tank bottom plate to form a non-penetrating V-shaped groove. A notch is formed below the right-angled trapezoidal protrusion, which can be inserted into the horizontal plate-like protrusion of the oil tank bottom plate, so that the self-shielding plate function of the oil tank bottom plate can be brought into play.

[0015] Specifically, the slope of the slope of the right-angled trapezoidal protrusion is 65-67.5°, and the groove angle is reduced as much as possible under the premise of facilitating welding and ensuring welding penetration.

[0016] Specifically, the height of the bottom surface of the right-angled trapezoidal protrusion is 10% to 15% of the thickness of the bottom plate of the oil storage tank.

[0017] Specifically, the width of the bottom surface of the right-angled trapezoidal protrusion is 20-25 mm.

[0018] Preferably, the slope of the slope structure of the replacement opening is the same as the slope of the right-angled trapezoidal protrusion of the repair base plate, and the lengths of the two slopes are equal, forming an isosceles inverted trapezoidal groove structure, that is, a non-penetrating V-shaped groove, and its groove angle is 45° to 50°.

[0019] The present invention also provides a T-joint pad, which is a T-shaped flat plate structure, which is placed at the T-shaped weld formed by the oil storage tank bottom plate and the repair bottom plate, and is spot-welded and fixed to the repair bottom plate.

[0020] In the present invention, the welding method does not involve a cross weld, and a T-joint pad is used in combination at the T-joint. The use of the T-joint pad can effectively reduce welding deformation during local repair of the bottom plate of a large flat-bottom storage tank and reduce stress concentration.

[0021] Specifically, the T-joint pad includes a transverse plate body and a longitudinal plate body. The transverse plate body has a length of 200-210 mm and a width of 50-60 mm; the longitudinal plate body has a length of 65-70 mm and a width of 50-60 mm; and the thickness is 4-6 mm.

[0022] The present invention also provides a welding process for repairing the bottom plate of an oil storage tank, comprising the following steps:

[0023] 1) Cut out a replacement area from the bottom plate of the oil storage tank to be repaired, and no cross welds appear around the replacement area;

[0024] 2) Processing the oil storage tank bottom plate into the oil storage tank bottom plate structure;

[0025] 3) placing the T-joint pad under the T-shaped weld appearing at the replacement opening;

[0026] 4) Processing the new steel plate into the repaired base plate and cleaning it before welding;

[0027] 5) Connecting the repair bottom plate to the oil tank bottom plate and the T-shaped pad respectively, wherein the upper end surface of the plate-like protrusion is spot welded under the bottom surface of the right-angle trapezoidal protrusion, and an assembly gap is reserved between the front end surface of the plate-like protrusion and the bottom side surface of the repair plate body;

[0028] 6) After preheating, welding is performed in the unpenetrated V-shaped groove, where the unpenetrated V-shaped groove is the area between the upper slope of each side surface of the replacement opening and the inclined surface of the right-angled trapezoidal protrusion of the repair plate body.

[0029] Specifically, in step 5), the T-joint pad is first fixed to the repair base plate, and then the repair base plate is fixed to the oil storage tank base plate. Preferably, the welding method is spot welding.

[0030] Specifically, in step 5), the assembly gap is 2 to 3 mm.

[0031] Specifically, in step 6), multiple passes of welding are performed, which include: manual arc welding for base welding, submerged arc automatic welding for filling and capping.

[0032] Specifically, induction heating or flame heating is used to preheat and interlayer heat the groove within a range of not less than 80 mm on both sides of the groove, and the temperature ranges of preheating and interlayer heating are 100-150° C. respectively.

[0033] Specifically, during root welding, 100% Ar shielding gas is used, the purity of Ar shielding gas is ≥99.99%, the welding current is 100-130A, the arc voltage is 21-22V, and the welding speed is 8-15cm / min; intermittent welding is selected for long welds.

[0034] Specifically, during submerged arc automatic welding filling, the welding current is 380-500A, the arc voltage is 28-32V, and the welding speed is 35-55cm / min.

[0035] Specifically, during cover welding, the welding current is 380-500A, the arc voltage is 28-32V, and the welding speed is 35-55cm / min.

[0036] Furthermore, after welding, the weld is visually inspected and non-destructively tested, and it is qualified if it reaches level II or above. Non-destructive testing uses X-ray flaw detection, and there are no defects such as incomplete penetration, incomplete fusion, pores, cracks, etc. in the weld, and there is no strip slag inclusion, and it is qualified if it reaches level II or above.

[0037] In general, the technical solution of the present invention can greatly reduce the material cost and workload, reduce welding deformation, and reduce stress concentration while ensuring performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is an assembly drawing of the oil storage tank bottom plate and the repair bottom plate provided by the present invention.

[0039] Figure 2 It is a schematic diagram of the top structure of the T-joint pad provided by the present invention.

[0040] Figure 3 It is an assembly drawing of the oil storage tank bottom plate, the repair bottom plate and the T-joint pad provided by the present invention.

[0041] Figure 4 It is an overall top view of the oil tank bottom plate after the repair bottom plate is replaced.

[0042] Attached Figure 1 , 2 , 3, and 4, the structures represented by each number are listed as follows:

[0043] 1. Bottom plate body, 101. Plate-shaped protrusion, 102. Slope structure, 2. Repair plate body, 201. Right-angle trapezoidal protrusion, 3. T-joint pad, 301. Transverse plate body, 302. Longitudinal plate body, 4. Spot welding position. DETAILED DESCRIPTION

[0044] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0045] In a specific embodiment, Figure 1 , 3 As shown, the oil tank bottom plate includes a bottom plate body 1, in which a replacement opening is cut, the bottom of each side of the replacement opening has a horizontal plate-like protrusion 101, and the upper part of each side of the replacement opening is a slope structure 102.

[0046] In a specific embodiment, Figure 1 , 3 As shown, the repair base plate includes a repair plate body 2, and a right-angled trapezoidal protrusion 201 is provided on the upper part of the side surface of the repair plate body 2.

[0047] In a specific embodiment, Figure 2 As shown, the T-joint pad 3 is a T-shaped flat plate structure, which includes an integrally formed transverse plate body 301 and a longitudinal plate body 302 .

[0048] Example 1

[0049] 1) Cut out the replacement area on the bottom plate of the oil storage tank to be repaired, and no cross welds appear in the replacement area;

[0050] 2) Processing the bottom plate of the oil storage tank to be repaired into the structure of the bottom plate of the oil storage tank provided by the present invention;

[0051] 3) Place a T-joint pad under the T-shaped weld that appears at the replacement opening;

[0052] 4) Process the new steel plate into the repair base plate and clean it before welding to remove rust, oil and other impurities within 50mm on both sides of the repair base plate to be welded;

[0053] 5) First, the T-joint pad is spot-welded to the repair bottom plate, and then the repair bottom plate is spot-welded to the oil tank bottom plate. The assembly method is as follows: the upper end surface of the plate-like protrusion 101 is pressed under the bottom surface of the right-angle trapezoidal protrusion 201, and an assembly gap is reserved between the front end surface of the plate-like protrusion 101 and the bottom side surface of the repair plate body 2, and an unpenetrated V-shaped groove is formed between the oil tank bottom plate and the repair bottom plate;

[0054] 6) After preheating, welding is performed in the unpenetrated V-shaped groove, which is the area between the upper slope of each side surface of the replacement opening and the inclined surface of the right-angled trapezoidal protrusion 201 of the repair plate body 2;

[0055] 7) After welding, the weld is visually inspected and non-destructively tested to ensure that it is qualified if it reaches level II or above.

[0056] In step 1), the bottom plate material of the oil storage tank to be repaired is Q235B steel, and the size of the replacement area is 3000mm×1000mm×10mm.

[0057] In step 2), the structure of the bottom plate of the oil storage tank is processed, such as Figure 1 , 3 As shown, its thickness t is 10 mm, the slope of its slope structure 102 is 22.5°, the thickness d of its plate-like protrusion 101 is 15% of the thickness of the bottom plate of the oil storage tank to be repaired, that is, 1.5 mm, and the width of the plate-like protrusion 101 is 25 mm.

[0058] In step 3), if Figure 2 As shown, the length L1 of the transverse plate body 301 of the T-joint pad is 200 mm, the length L2 of the longitudinal plate body is 70 mm, the width is 60 mm, and the thickness is 4 mm.

[0059] In step 4), the slope of the slope of the right-angled trapezoidal protrusion 201 of the repaired bottom plate is 22.5°, and its material is the same as that of the bottom plate of the oil storage tank, that is, Q235B steel.

[0060] In step 5), if Figure 1 , 3 As shown, the groove angle θ of the V-shaped groove that has not been penetrated is 45°, the reserved assembly gap δ is about 2.5 mm, and the spot welding positions 4 are respectively located on the connecting surface between the T-joint pad and the repair bottom plate, and on the connecting surface between the repair bottom plate and the bottom plate of the oil storage tank.

[0061] In step 6), multiple passes of welding are performed, including manual arc welding for base welding, submerged arc automatic welding for filling and capping.

[0062] The induction heating method is used to preheat and interlayer heat the range of 80mm on both sides of the groove, and the temperature of preheating and interlayer heating is 150℃.

[0063] For manual arc welding, choose Ф3.2 / Ф4.0mm low-hydrogen sodium type E4315 electrode.

[0064] Submerged arc automatic welding uses Ф4.0mm H08MnA welding wire.

[0065] Submerged arc automatic welding is used for cover welding.

[0066] During root welding, use 100% Ar shielding gas, the purity of Ar shielding gas is ≥99.99%, the welding current is 125A, the arc voltage is 22V, and the welding speed is 12cm / min; according to the 3000mm long weld, the 400mm interval welding 200mm cycle intermittent welding method is selected.

[0067] When submerged arc automatic welding is used for filling, the welding current is 480A, the arc voltage is 30V, and the welding speed is 50cm / min.

[0068] During cover welding, the welding current is 480A, the arc voltage is 30V, and the welding speed is 50cm / min.

[0069] When welding, follow the principle of short first and then long, and use intermittent welding for long welds.

[0070] In step 7), after welding, Figure 4 As shown. The weld was visually inspected, and the flatness and deformation of the entire bottom plate were checked. No obvious concave and convex deformation was found. X-ray flaw detection was used for non-destructive testing, and the test results are as follows:

[0071]

[0072] From the above results, it can be seen that the nondestructive testing results of the welding joint are qualified.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An oil storage tank bottom plate, comprising a bottom plate body (1), wherein the bottom plate body (1) has a replacement opening cut out therein, characterized in that: The bottom of each side surface of the replacement opening has a horizontal plate-shaped protrusion (101), and the upper part of each side surface of the replacement opening is a slope structure (102).

2. The oil storage tank bottom plate according to claim 1, characterized in that: One or more of the following conditions are met: The replacement opening is rectangular; The slope of the slope structure (102) is 65-67.5°; The thickness of the plate-shaped protrusion (101) is 10% to 15% of the thickness of the base plate body (1); The width of the plate-shaped protrusion (101) is 20 to 25 mm.

3. A repair base plate, comprising a repair plate body (2), characterized in that: A right-angled trapezoidal protrusion (201) is provided on the upper portion of the side surface of the repair plate body (2).

4. The repair base plate according to claim 3, characterized in that: One or more of the following conditions are met: The slope of the slope of the right-angled trapezoidal protrusion (201) is 65-67.5°; The height of the bottom surface of the right-angled trapezoidal protrusion (201) is 10% to 15% of the thickness of the bottom plate of the oil storage tank; The width of the bottom surface of the right-angled trapezoidal protrusion (201) is 20 to 25 mm.

5. A T-joint pad, characterized in that: It is a T-shaped flat plate structure, which is spot welded at the T-shaped weld formed by the oil tank bottom plate and the repair bottom plate.

6. The T-joint pad according to claim 5, characterized in that: The T-joint pad comprises a transverse plate body (301) and a longitudinal plate body (302); the transverse plate body (301) has a length of 200 to 210 mm and a width of 50 to 60 mm; the longitudinal plate body (302) has a length of 65 to 70 mm and a width of 50 to 60 mm; and a thickness of 4 to 6 mm.

7. A welding process for repairing the bottom plate of an oil storage tank, characterized in that: The following steps are involved: 1) A replacement area is cut out from the bottom plate of the oil storage tank, and no cross welds appear around the replacement area; 2) Processing the bottom plate of the oil storage tank to be repaired into the oil storage tank bottom plate structure according to claim 1 or 2; 3) placing the T-joint pads as claimed in claim 5 or 6 under the T-shaped welds around the replacement opening; 4) Processing the new steel plate into the repaired base plate as claimed in claim 3 or 4, and performing pre-welding cleaning; 5) connecting the repair bottom plate to the oil tank bottom plate and the T-joint pad respectively, wherein the upper end surface of the plate-like protrusion (101) is spot welded under the bottom surface of the right-angle trapezoidal protrusion (201), and an assembly gap is reserved between the front end surface of the plate-like protrusion (101) and the bottom side surface of the repair plate body (2); 6) After preheating, welding is performed in the unpenetrated V-shaped groove, wherein the unpenetrated V-shaped groove is the area between the upper slope of each side surface of the replacement opening and the inclined surface of the right-angled trapezoidal protrusion (201) of the repair plate body (2).

8. The oil tank bottom plate repair welding process according to claim 7 is characterized in that: In step 5), the T-joint pad is first connected to the repair bottom plate by spot welding, and then the repair bottom plate is fixed to the oil storage tank bottom plate by spot welding; the assembly gap is 2 to 3 mm.

9. The oil tank bottom plate repair welding process according to claim 7 is characterized in that: In step 6), multiple passes of welding are performed, which include: manual arc welding for base welding, submerged arc automatic welding for filling and capping.

10. The oil tank bottom plate repair welding process according to claim 9 is characterized in that: Use induction heating or flame heating to preheat and interlayer heat within a range of not less than 80mm on both sides of the groove. The temperature ranges of preheating and interlayer heating are 100-150℃ respectively. When welding the root, use 100% Ar shielding gas, the purity of Ar shielding gas is ≥99.99%, the welding current is 100-130A, the arc voltage is 21-22V, and the welding speed is 8-15cm / min; for long welds, choose intermittent welding; When submerged arc automatic welding is used for filling, the welding current is 380-500A, the arc voltage is 28-32V, and the welding speed is 35-55cm / min; When cap welding, the welding current is 380~500A, the arc voltage is 28~32V, and the welding speed is 35~55cm / min.

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